Optical wood-bark segregator

Abstract

A process of separating wood chips according to their bark content by orienting them between a light source and light detector, measuring the amount of light transmitted through each chip, and separating the bark-laden chips from the bark-free chips on the basis of their light transmittance. An apparatus for separating wood chips according to their bark content, comprising a light source, a light detector, means for properly orienting the wood chips between the light source and detector, and means for differentiating between bark-laden chips and bark-free chips on the basis of their light transmittance.

Having disclosed our invention, we claim: 
     
       1. A process of separating wood fiber chips from wood-bark fiber chips and bark fiber chips comprising: a. orienting a mixture of wood chips comprising wood fiber chips, wood-bark fiber chips, and bark fiber chips in a detecting zone between a light source and a light-detecting means;   b. transmitting a beam of light from said light source through the thickness of said wood chips and detecting said beam of light with said light-detecting means;   c. passing said wood chips through a separating zone where said separating zone and said detecting zone constitute a straight path for said wood chips to travel;   d. separating said wood fiber chips from said wood-bark fiber chips and said bark fiber chips by causing said wood-bark fiber chips and said bark fiber chips to deviate from said straight path in response to the relative amount of light transmitted through said wood chips, the amount of light transmitted through said wood fiber chips being the greatest.   
     
     
       2. The process of claim 1 wherein the wood chips are subjected to a preseparation prior to the orienting step to remove contaminants such as dirt, grit, soils, and small bark fiber chips. 
     
     
       3. The process of claim 1 wherein the wood chips are caused to travel through the straight path by gravity. 
     
     
       4. The process of claim 1 wherein the wood-bark fiber chips and the bark fiber chips are caused to be deflected from the straight path by a blast of air directed perpendicularly to said straight path. 
     
     
       5. An apparatus for differentiating between components of a mixture of wood chips comprising wood fiber chips, bark fiber chips, and wood-bark fiber chips comprising: a. light-source means;   b. detecting means adjacent said light-source means for detecting light from said light-source means;   c. means for orienting said wood chips comprising an intermediate compartment having a first wall and a second wall, said first and second walls being spaced apart so as to allow a single layer of wood chips to pass in a straight path between, each of said walls having a plurality of holes positioned so that light will pass through a hole in said second wall, through each wood chip in said intermediate compartment, through a hole in said first wall, and to said detecting means; and   d. differentiating means connected to said detecting means for differentiating between light transmitted through the wood fiber chips, wood-bark fiber chips, and bark fiber chips.   
     
     
       6. An apparatus as described in claim 5 further comprising a preseparation means adjacent the upstream end of said orienting means for removing contaminants contained in said wood chips before said wood chips pass through said orienting means. 
     
     
       7. An apparatus as described in claim 5 further comprising a separating means for separating said wood fiber chips from said wood-bark fiber chips and said bark fiber chips in response to said differentiating means, said separating means being adjacent the downstream end of said orienting means. 
     
     
       8. An apparatus as described in claim 5 wherein the light-source means comprises a plurality of light sources mounted on the outside of said second wall, and wherein the detecting means comprises a number of light detectors equal to the number of light sources mounted on the outside of said first wall. 
     
     
       9. An apparatus as described in claim 8 wherein the separating means comprises a first plurality of openings in the second wall immediately below said light sources, said openings being equal in number to the number of light sources and larger than the wood chips; a plurality of air nozzles mounted in the first wall directly opposite said first openings; and means connected to said air nozzles and differentiating means for creating an air blast in response to said differentiating means when bark fiber chips and wood-bark fiber chips are detected by said detecting means. 
     
     
       10. An apparatus as described in claim 9 further comprising a frame assembly, a center support rigidly attached to said frame assembly, a circular ring plate rotatably attached to said center support to which the first and second walls are concentrically attached, said first wall having at the bottom a second plurality of openings through which the wood fiber chips are removed from the intermediate compartment, means for rotating said circular ring plate, a first collecting means adjacent said second plurality of openings for collecting said wood fiber chips, and a second collecting means adjacent said first plurality of openings for collecting said wood-bark fiber chips and said bark fiber chips. 
     
     
       11. An apparatus as described in claim 10 further comprising a preseparation means for removing contaminants contained in the wood chips wherein said preseparation means comprises a circular vibrating screen having perforations and a peripheral edge that in adjacent to said intermediate compartment, a vibrating plate positioned below and attached to said circular vibrating screen, said vibrating plate being concentrically attached rigidly to said center support, and a vibrating means attached to said circular vibrating screen and said vibrating plate to vibrate said circular vibrating screen and said vibrating plate.